1. College of Materials Science and Engineering Xi'an University of Architecture and Technology Xi'an Shaanxi 710055 P. R. China
2. State Key Laboratory of Advanced Refractories Sinosteel Luoyang Institute of Refractories Research Co. Ltd. Luoyang 471039 P. R. China
3. Science and Technology on Thermostructure Composite Materials Laboratory Northwestern Polytechnical University Xi'an Shaanxi 710072 P. R. China